1. Field of the Invention
This invention relates to a multistage discharge type rotary vacuum pump having a multiplicity of discharge stages with a single rotor and stator set.
3. Description of the Prior Art
In most conventional rotary vacuum pumps, only one working chamber is formed in a cylinder chamber as in the Gaede type pump.
Heretofore, in order to obtain high vacuum with this type of rotary vacuum pump, multistage discharge was conducted by connecting a plurality of rotor and stator sets in a tandem through a common rotor shaft and connecting a discharge port of an upstream stage to an inlet port of a downstream stage of each pump.
However, this kind of structure requires a large size and a complicated apparatus and requires an increased driving force.